The present invention relates to a method and apparatus for monitoring, or mapping, the neutron flux in nuclear reactors.
The monitoring of a nuclear reactor, such as, for example, a pressurized water reactor, includes the production of flux maps when the reactor is operating in the low output power range during initial plant start-up and following each refueling operation. In order to create sufficient neutron activity to obtain a flux map with known mapping assistance, it is necessary to increase the reactor output power to 4-5 percent of rated power. Such power increase for the purpose of enabling a flux map to be produced increases the possibility of an inadvertent reactor trip and causes steaming, which wastes condensate water. It would therefore be desirable to be able to obtain accurate flux maps with the reactor operating at zero power output.